The present invention relates to electric energy meters, and more particularly to the provision of an optical communications light shield in an optical communications link.
Present day electric energy meters and registers have greatly expanded capabilities and are being called upon to provide additional functions beyond simple indications of kilowatt hour consumption and kilowatt demand. Modern electric meters are often equipped with electronic time of use registers. These registers require a means to read time of use billing data acquired by, and stored in, the meter and also to provide for the programming of billing parameters. This is commonly achieved by means of an optical communications link. In previous designs this link was commonly implemented by mounting a light emitter and light detector in the transparent cover of the energy meter so that it could be read by the meter reader through use of a detachable magnetic coupler. The light emitter and light detector in such cover-mounted arrangements are connected to the register electronic circuitry by means of a cable extending between the cover and register electronics. Such an arrangement is cumbersome because the cable must be connected to the register assembly prior to the installation of the cover. Also, the cable makes it difficult to remove the cover in order to gain access to the inside of the meter for maintenance and service procedures, including access for the actuation of certain test switches frequently mounted on the meter face in electronic energy meters. In addition, power utilities commonly follow the practice of periodically washing meter covers in commercial type dishwashers. Such a practice can be difficult in the presence of cover mounted electronics, and can injure the electronic components. As a result, it is desirable to eliminate the cover mounted electronic components in electric energy meter while at the same time continuing to provide for the use of an optical communications link to access the register from outside the meter case to read the register and also to program billing parameters into the register. However, with such an arrangement it becomes necessary to provide good optical shielding from ambient light of the optical communications link, especially in meters mounted in direct sunlight.